Window Sill stock

I'm replacing several rotted sills for a friend, and the only stock I can find at both HD and my local yard is close, but not a great match, especially where it meets the casing. The yard tells me "this is standard sill stock, it's all we carry". Anyone know of a listing (online ideally) where I can try to find a better match?

(post #74361, reply #5 of 8)

I just got finished doing one, and I know what you mean about close but not exact. Actually, I started out to do a common sill under a pair of DH windows, with rot under one end, but ended up doing just one side. I removed the trim nailed to the stud between the two windows, then used the recip to make a smooth cut dead center. The part of the sill under the second window was sound, and this was upstairs facing the woods, so I figured I could suffer the "but not exact.". It was rot at the joint between the sill and the bottom of the casing on the other side of the first window that had started the mess, and there was some rot at the bottom of the trim between windows too.

The old sill came out in small pieces with the aid of a chisel and hammer, splitting it out in pieces from drip edge inward. Once I got inside of the siding, I used the recip to make multiple cuts inward toward the nose inside, took out more chunks, then split horizontally into the pieces stuck to the nails through the jambs and inside apron and pulled the pieces off the nails with pliars. The ends of the nails I cut with wire cutters and the recip. What I wanted to avoid was having to tear off the stained woodwork inside the house, and this made things more difficult.

The local yard provided the sill (close but not exact), preprimed, at ten bucks a foot, which I think is more than it ought to be, but, in the interests of time and weather....

I made liberal use of the saw (radial; table would work as well) plus recip to cut to length and the bullhorns on the ends, cut a small dado near the inside for the plastic seal that fits up into the slot under the window sash, and trim the upper inside edge so it would fit flat up under the nose. The dado slots in the jambs weren't cut for a tight fit, vertically, so supporting the inside edge of the new sill was a problem. I solved that by trial and error cuts off the height of a bevelled piece of old casing, reducing the height until the new sill was seated up snugly under the nose. Then I nailed the piece of casing to the framing under the sill and nailed the sill to that piece, sinking the nails in the slot I had cut for the window seal.

Of course, things would have been easier if I had planned on replacing nose and apron, with all the finishing work that would have entailed. That would have opened up the bottom of the window assembly for easy access to the old sill and made support of the new sill that much easier.

I bothers me that the fix I had effected left unsealed the joint between the new sill and the bottoms of the side pieces into which the windows pop afterward. I used caulk applied at the bottom of the sides, but who knows how long that will last. Wind-driven rain could ultimately find its way laterally under the edge of the sill. I also used caulk to seal between the butt ends of the two adjacent sills, and primed all cut surfaces before installation. Still, I guess all such repairs are just temporary.

This was my first experience at sill replacement. I still have a common sill under a triple DH to do, plus at least half of a double DH. So if someone with experience at this wants to chime in on how to do it differently (presumably better). I'm all ears.